Compositions useful for repairing damaged teeth in, situ are known in the art as direct filling materials, and include alloys and resin composites. Amalgam dental fillings are being increasingly replaced with dental composites that more closely match the color and appearance of the natural tooth. These composites generally contain an organic resin with a microparticle filler. Most systems incorporate a light- or UV-curable polymeric resin, such as a diglycidylmethacrylate of bisphenol. A (BIS-GMA), triethyleneglycol dimethacrylate (TEGDMA) or a urethane dimethacrylate (UDMA). The filler particles are typically barium silicate glass, quartz, or zirconium silicate, combined with small colloidal silica particles.
Increasingly, composite formulations have also included glass ionomers, which are known to release fluoride. Cariostatic properties are attributed to fluoride and thus, glass ionomer cements are associated with favorable cariostatic behavior. Another important aspect of glass ionomer cements is the strong clinical adhesion of such cements to tooth structure, thus providing highly retentive restorations.
One disadvantage associated with glass ionomer cement materials is they are generally supplied as a two-component system, with one part being in liquid form and the other in powder form. The liquid is typically a polyacrylic acid or its co-polymer in water. The powder part is commonly a fluoroaluminosilicate (FAS) glass, with an exemplary formula ofSiO2—Al2O3—CaF2—NaAlF6—AlPO4 
Two-component packaging is generally necessary because a glass ionomer powder can readily react with polyacrylic acid or its co-polymer in the presence of water. As such, the glass ionomer powder is packaged separately from the polyacrylic acid, in order to have a shelf-life or storage life. Alternatively, a powder form of both the polyacrylic acid and the glass ionomer may be premixed and water added just prior to use. Some paste-paste versions of the glass ionomer cements have also been developed. In those cases, however, the glass ionomer powders are mixed with a non-reactive component to form one paste and the polyacrylic acid component comprises the other paste. In any event, the foregoing examples provide for two-component dental resin restorative compositions that are mixed just prior to use. The mixture will undergo self-hardening in the dark due to the ionic reaction between the acidic repeating units of the polyacrylic acid and cations leached from the glass.
One shortcoming of the conventional glass ionomer cements is that they can be technique sensitive. For example, their performance can be affected by the mixing ratio, as well as the manner of mixing. Additionally, they are quite brittle, as evidenced by their low flexural strength and tend to undergo fracture quite readily. Therefore, it would be desirable to attain a glass ionomer composition as a one-component dental resin restorative composition that does not require any premixing just prior to use. It would be desirable that this composition be light curable, mechanically strong, stable, and capable of releasing fluoride.